Wednesday, 5 November 2014
What is PGD?
PGD stands for Pre-implantation genetic diagnosis and is a genetic screening that can be performed in IVF treatments. During IVF treatment, the female egg is fertilized with the sperm in a laboratory environment outside the human body. The embryo is usually observed for 5 days for desirable progress before implantation back tothe female uterus. This 5-day period allows a genetic screening to be performed on the embryo in order to determine if the embryo has a genetic disease passed from the parents. This ensures that the embryo selected for transfer is free from genetic disease.
Humans have 23 pairs of chromosomes for a total of 46. 22 of these pairs are called autosomes and are the same for both males and females. The 23rd pair is the gender chromosome, which is different in males and females. Typically, in PGD analysis, 5-9 pairs of chromosomes are analysed for the most common genetic diseases. This type of genetic testing enables genetic disease like Monosomy, Trisomy, Down’s syndrome to be screened. In some cases, PGD is performed to enable gender selection for families having a preference for a certain baby gender. It is also worth to note that some genetic diseases only affect a certain gender. For example genetic diseases like Duchenne muscular dystrophy or Haemophillia A only affect males, hence making it important to know the baby gender before implantation.
PGD is a general name given for all pre-implantation genetic testing and many other types of genetic testing can also be performed. The type of genetic testing to be performed can be decided based on the family history of genetic diseases.
Only drawbacks of PGD is that during the biopsy phase (a cell has to be removed from the embryo to enable genetic testing) damage could occur inhibiting the development of the embryo. In addition, despite having extremely high success rates (over 99%), the PGD screening may end up being inconclusive.
To summarize, in general families with genetic disorders, older women, women who had several miscarriages and couples wishing to do gender selection usually choose to proceed with PGD. Performing PGD helps avoid abortion when a genetic anomaly is found later in pregnancy.